Civil Engineering Reference
In-Depth Information
Angle of tilt
°
3.0
90
80
2.5
70
60
View along line of
intersection
2.0
50
40
30
Wedge factor
K
= sin
/ sin (½
)
10
20
for
>½
1.5
1.0
Two dimensional plane failure
when for
<½
0.5
0
0
20
40
60
80
100
120
140
160
180
Included angle of wedge
— degrees
Figure 7.5
Wedge factor
K
as a function of wedge geometry.
pressure distribution assumed for this analysis is
based upon the hypothesis that the wedge itself
is impermeable and that water enters the top of
the wedge along lines of intersection 3 and 4 and
leaks from the slope face along lines of intersec-
tion 1 and 2. The resulting pressure distribution
is shown in Figure 7.6(b)—the maximum pres-
sure occurring along the line of intersection 5 and
the pressure being zero along lines 1, 2, 3 and 4.
This is a triangular pressure distribution with the
maximum value occurring at the mid-height of
the slope, with the estimated maximum pressure
being equal to
(
2
γ
w
H)
. This water pressure dis-
tribution is believed to be representative of the
extreme conditions that could occur during very
heavy rain and the slope is saturated.
The two planes on which sliding occurs are
designated A and B, with plane A having the
shallower dip. The numbering of the five lines of
intersection of the four planes defining the wedge
is as follows:
Line 1
Intersection of plane A with the slope
face
Line 2
Intersection of plane B with the slope
face
Line 3
Intersection of plane A with upper
slope surface
Line 4
Intersection of plane B with upper
slope surface
Line 5
Intersection of planes A and B
It is assumed that sliding of the wedge always
takes place along the line of intersection
numbered 5, and its factor of safety is given by
